University of Arkansas, FayettevilleScholarWorks@UARKBiomedical Engineering Undergraduate HonorsTheses Biomedical Engineering

5-2016

Optimized Protocol for Measuring 2-NBDGUptake as a Cellular Marker of Glycolytic DemandDrew FolgmannUniversity of Arkansas, Fayetteville

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Recommended CitationFolgmann, Drew, "Optimized Protocol for Measuring 2-NBDG Uptake as a Cellular Marker of Glycolytic Demand" (2016).Biomedical Engineering Undergraduate Honors Theses. 31.http://scholarworks.uark.edu/bmeguht/31

Table of Contents

Abstract …………………………………………………………………………………………..2

Introdcution ……………………………………………………………………………..….....3–5

Methods and Materials ………………………………………………………………..…..….5–8

Cell Viability Study ...................................................................................................... 5 -6

2-NBDG Concentration vs. Cell Viability Study …………………………………...….6-7

2-NBDG Uptake Study …………………………………………………………...…….7-8

Image Analysis ………………………………………………………………………….8

Results ……………………………………………………………………………………...…9-13

Cell Viability Study ………………………………………………………………………9

2-NBDG Concentration vs. Cell Viability Study .............................................................10

2-NBDG Uptake Study ………………………………………………………………10-13

Discussion and Conclusions ………………………………………………………………..14-15

Future Directions ……………………………………………………………………………....15

Acknowledgements ……………………………………………………………………….....…16

References …………………………………………………………………………………...17-18

Appendices ………………………………………………………………………………….19-20

Appendix A: Supplementary Data …………………………………………………..19-20

2

Abstract:

2[N-(7-nitrobenz-2-oxa-1,2-diaxol-4-yl)amino]-2-deoxyglucose (2-NBDG) a

fluorescently tagged analog of FDG is ideal for in vitro studies and imaging. 2-NBDG has been

proven to be an adequate marker for glucose uptake in many different types of cells [1].

However, across the spectrum of 2-NBDG use a lack of consensus is observed for the following

questions. What is the ideal time to fast cells to optimize cellular uptake of 2-NBDG? Also, what

is the ideal concentration of 2-NBDG to be used when quantifying glucose uptake? Finally, what

is the effect of serum on the uptake of 2-NBDG? To answer these questions and understand

glucose uptake, the Balb/cfC3H 4T07 murine breast cancer cell line was fasted at varying time

points between 0 and 150 minutes. Cell viability was evaluated for these time points using

Promega’s (Madison, WI) CellTiter-Glo® luminescent assay. Cells were also plated into 35mm

glass bottom dishes, incubated for 24 hours, and fasted for varying times between 0 and 150

minutes. 400µM of 2-NBDG was introduced for 20 minutes and uptake was quantified using

fluorescence microscopy. The peak of cell viability and glucose uptake was compared to find the

optimal fasting time. Once fasting studies were complete, cells were fasted according to ideal

conditions and concentration dependency of 2-NBDG was investigated. It was found that 4T07

cell viability is significantly decreased by 60 minutes of fasting cells in DMEM (-) glucose in the

absence of 10% serum. The addition of 10% serum to the DMEM (-) glucose prolongs the

fasting range to at least 150 minutes. 2-NBDG uptake is higher with the addition of 10% serum

to DMEM (-) glucose in 20 minute fasting conditions. Also, 400µM 2-NBDG is the ideal

concentration to optimize cell viability, cost effectiveness, and uptake.

3

Introduction:

Cancer cells have been shown to have an increased amount of glucose uptake relative to

normal cells [1]. Currently Positron Emission Tomography (PET) is used to detect areas of high

glucose tracer uptake [2]. The most commonly used tracer in the clinical diagnosis of cancer is

radiolabeled fluorodeoxy-glucose (FDG). FDG-PET, however, is complicated to use in vitro due

to its level of radiation exposure [3]. 2[N-(7-nitrobenz-2-oxa-1,2-diaxol-4-yl)amino]-2-

deoxyglucose (2-NBDG) a fluorescently tagged analog of fluorodeoxy-glucose (FDG) is ideal

for in vitro studies and imaging. The use of 2-NBDG allows researchers to quantify glucose

uptake without using radioactive tracers such as FDG. It can be easily quantified through flow

cytometry, fluorescence microscopy, or fluorescence plate readings. 2-NBDG has been proven

to be an adequate marker for glucose uptake in many different types of cells [1]. Roger O’Neil et

al. used 2-NBDG to look at glucose uptake of breast cancer and liver cancer cell lines [4].

Nathalie Rouach et al. used 2-NBDG to study the uptake of glucose in perivascular astrocytes [5].

These are just a few examples of the scope of 2-NBDG use. To uptake 2-NBDG effectively cells

must be fasted, the time(s) for which to do so vary from study to study [1, 4-7]. Another

interesting characteristic of 2-NBDG is that when added in high concentrations 2-NBDG 6-

Phosphate can accumulate and kill the cell [6]. The point at which 2-NBDG concentration begins

to inhibit the uptake of glucose is currently unknown. The effects of fetal bovine serum on 2-

NBDG uptake will also be investigated. High concentrations of fetal bovine serum (FBS) in

culture media has shown to significantly impair uptake of FDG [7]. The data obtained from these

experiments will develop a standard for 2-NBDG uptake studies across the scientific community.

2-NBDG is a very important biomolecule that has potential applications in many areas of

medical research.

4

Once the fasting times of murine Balb/cfC3H cell lines are optimized this knowledge will

be applied to human breast cancer cells. These data sets will allow for direct applications in

clinical imaging systems. Ex Vivo cancerous tissues can be fasted and imaged according to the

findings of this study; this will give physicians a stronger diagnostic tool to identify breast cancer

and develop treatment plans.

Project Overview: Some of the major questions we seek to answer are:

1. What are the ideal fasting time point(s) for optimal uptake of 2-NBDG?

2. Does 2-NBDG uptake depend on the addition of Fetal Bovine Serum metabolites?

3. After fasting, what concentration of 2-NBDG is optimal for uptake of cells with differing

glycolytic demand?

To find the ideal fasting time point(s) of murine breast cancer cells, I first needed to

determine the ideal cells for testing. Previous studies have shown good glucose uptake in select

Balb/cfC3H lines (66cl4, 67NR, 4T07, 4T1, and 168FARN) [1]. To start the 4T07 cell line was

deemed to be ideal because of its high glycolytic demand but non metastatic potential.

The 4T07 cells were seeded into 96- well plates for cell viability studies or 35mm glass

bottom dishes for imaging. After 24 hours all media was removed and washed with Phosphate

Buffer Solution (PBS) to ensure removal of all glucose media. Media with glucose was added

into control wells/dishes and media without glucose (+/- serum) was added into respective test

wells. The first set of test trials did not include fetal bovine serum in the glucose free fasting

media. The second set of test trials did include fetal bovine serum in the glucose free fasting

media. The cells were placed in the incubator for varying fasting times between 0 and 150

minutes. Once each plate’s respective fasting time was up the cell viability was assessed or 2-

NBDG was added for uptake quantification. The 2-NBDG uptake quantification plates/dishes

5

were then incubated for 20 minutes. Following, all 2-NBDG was removed and washed twice

with PBS before quantification using fluorescence microscopy.

To study the effects of varying concentrations of 2-NBDG, cells were fasted according to

the protocol above. A wide range of 2-NBDG concentrations were added for 20 minutes and

glucose uptake was analyzed using a fluorescence plate reading.

Materials and Methods

Cell Viability Studies:

Cell Plating:

4T07 cells were obtained, thawed, and placed into a 75cm2 cell flask with media

containing glucose. Dulbecco’s Modified Eagle Medium from Thermo Fisher Scientific

(Waltham, MA). It was supplemented with L-Glutamine, Fetal Bovine Serum, Nonessential

Amino Acids, and Penicillin Streptomycin. After three passages to remove Dimethyl sulfoxide

(DMSO) freezing agent the cells were ready to be used for experimentation. The cells were

passaged according to a standardized procedure handed down from Duke University. Cells were

counted in a hemocytometer and centrifuged at 950 revolutions per minute for 4 minutes at 4

degrees Celsius. The cells were then re-suspended to achieve 10,000 cells in a volume between

100- 200 microliters. This is the recommended working volume of a standard 96-well plate.

10,000 cells was hypothesized to give a strong enough luminescent signal and proper confluency

for cell viability assay readings. The cells were seeded onto a white walled, flat, clear bottom 96-

well plate. The white walls prevent cross talk between wells and also provide a stronger

luminescent signal for more accurate detection. Once the cells were seeded at the appropriate

dilution with complete DMEM the plate was placed in an incubator at 37 degrees Celsius for 24

hours.

6

Fasting and Assay Protocol

After the 24 hour incubation period all DMEM was removed, and all wells were washed

with PBS to ensure removal of glucose media. 100 microliters of DMEM (+) glucose or DMEM

(-) glucose (+/-) 10% Fetal Bovine Serum (FBS) was added to the wells as indicated below.

Figure 1: Indicating the locations of the test variables on the 96- well plate for the cell

viability studies.

Source:http://users.path.ox.ac.uk/~scobbold/tig/

After all DMEM (+/-) glucose was added to appropriate wells the plates were placed in the

incubator for 0, 30, 60, 90, 120, 150 minutes. While the plates were incubating the Promega Cell

Titer-Glo® reagent was prepared. Once the fasting duration was complete for each respective

plate 100 microliters of Cell Titer-Glo® reagent was added in addition to the 100 microliters of

DMEM (+/-) glucose. Cell lysis was induced to allow the assay agents to attach to the cell ATP

by placing the sample on an orbital shaker for 2 minutes prior to measuring luminescence.

Luminescence was measured using a BioTek Synergy HT plate reader.

2-NBDG Concentration vs. Cell Viability Study:

4T07 cells were plated on white 96-well plates. The ideal fasting time was determined

from the cell viability study and was used to fast the cells according to the same protocol as

above. Following the fast 2-NBDG was added according to the diagram below at concentrations

between 50 and 400µM:

LEGEND: 10,000 cells w/Glucose

10,000 cells w/o Glucose

No Cells Background

Luminesce w/Glucose Media

No Cells Background

Luminesce w/o Glucose

Media

7

Figure 2: Indicating the locations of the test variables and their respective 2-NBDG

concentrations by row on the 96- well plate. Row A contained 50µM of 2-NBDG in glucose free

(columns 1-3) and glucose (columns 9-11) conditions. Row C contained 100µM of 2-NBDG in

glucose free (columns 1-3) and glucose (columns 9-11) conditions. Row E contained 250µM of

2-NBDG in glucose free (columns 1-3) and glucose (columns 9-11) conditions. Row G contained

400µM of 2-NBDG in glucose free (columns 1-3) and glucose (columns 9-11) conditions.

Column 7 contained cells without 2-NBDG in glucose free (rows E+F) and glucose (rows B+C)

conditions.

Image source: http://users.path.ox.ac.uk/~scobbold/tig/

Once fasting was completed all media and 2-NBDG was removed. Each test well was then

washed twice with Phosphate-Buffered Saline (PBS). Following, 100µL of the Cell Titer-Glo®

reagent was added to each well. Cell lysis was induced to allow the assay agents to attach to the

cell ATP by placing the sample on an orbital shaker for 2 minutes prior to measuring

luminescence. Luminescence was measured using a BioTek Synergy HT plate reader.

2-NBDG Uptake:

Once the assessment of cell viability at all fasting time points and the ideal concentration

was determined, glucose uptake was evaluated. 200,000 4T07 cells were plated on 35mm MaTek

glass bottomed dishes. The cells were fasted using the same methods listed above in both (+/-)

10% FBS conditions. When each dish reached its respective fasting time 2-NBDG was

introduced for 20 minutes at a concentration of 400µM. The concentration of 2-NBDG remained

constant at 400µM for all samples, this was to rule out the effects of 2-NBDG concentration

dependent uptake variability. Each dish was then removed from the incubator and washed twice

LEGEND: Cells w/Glucose + 2-NBDG

Cells w/o Glucose + 2-NBDG

Cell Luminesce w/Glucose Media

Cell Luminesce w/o Glucose Media

Row A:50µM

Row C:100µM

Row E:250µM

Row G:400µM

8

with PBS. To quantify 2-NBDG fluorescence a Nikon (Melville,NY) Eclipse ti-s inverted

microscope fitted with a DS-fi2 camera was used for image collection. 2-NBDG has an

excitation/emission spectra of 465/540nm respectively.

Image Analysis:

Fluorescence intensity images were analyzed using MATLAB. The background intensity

from each image was subtracted out to yield the fluorescence of the cells. A background image

was taken on every day cells were imaged. This was to account for day to day variability of the

fluorescence signal. A histogram was constructed for the sum of each group of test sample

images.

9

Results:

4T07 cell viability was evaluated in DMEM (-) glucose and DMEM (+) glucose both (+/-) serum

as seen in Figure 3. Cell viability was significantly decreased at 60 minutes in the DMEM (-)

glucose without serum. There wasn’t a significant difference between cells fasted in DMEM (-)

glucose or DMEM (+) glucose with the addition of 10% serum at all times between 0 – 150

minutes.

Cell Viability Studies:

Figure 3:A) In the absence of serum, viability of the cells fasted for 60 minutes in DMEM (-)

glucose was significantly lower (p<0.001) as well as for all time points following. B) 4T07 cell

viability is comparable for all fasting times between 0-150 minutes in DMEM (+/-) glucose with

the addition of 10% serum to the media. All data sets were collected on a white 96-well plate.

Error bars indicate the standard deviation of the samples. * Indicates a significant difference with

an alpha = 0.05.

10

2-NBDG Concentration vs. Cell Viability Study: 4T07 cell viability was evaluated for varying 2-NBDG concentrations (0µM, 50µM,

100µM, 250µM, 400µM) in the absence of serum. Figure 4 shows the higher cell viability in

DMEM (-) glucose as 2-NBDG concentration increased. There was no significant difference

between the cell viability in DMEM (-) glucose and DMEM (+) glucose with 250µM and

400µM 2-NBDG.

Figure 4: Cell viability is significantly higher (p = 0.03) in a 400µM 2-NBDG solution when

compared to a 50µM solution. All samples were fasted for 10 minutes in DMEM (-) glucose then

incubated with 2-NBDG with DMEM (-) glucose for 20 minutes. The control samples contained

cells in their respective media. All samples were collected on a white 96-well plate. Error bars

indicate the standard deviation of the samples. * Indicates a significant difference with an alpha

= 0.05

2-NBDG Uptake:

4T07 cells were imaged after 20 minutes of fasting in DMEM (-) glucose (+/-) serum.

The addition of 10% serum to the DMEM (-) glucose fasting media increased 2-NBDG uptake as

*

11

indicated in Figure 5. The 2-NBDG uptake of 4T07 cells in both (+/-) serum for various fasting

durations is shown in Figure 6.

Figure 5: 200,000 4T07 cells were plated in 35mm glass bottom dishes and cultured for 24

hours prior to use. A Nikon (Melville,NY) Eclipse ti-s inverted microscope fitted with a DS-fi2

camera was used for image collection. 2-NBDG has an EX/EM of 465/540nm respectively. A)

4T07 cells incubated for 20 minutes with 400µM 2-NBDG in DMEM (-) glucose with the

addition of 10% serum. B) 4T07 cells incubated for 20 minutes with 400µM 2-NBDG in DMEM

(-) glucose. C) A histogram of fluorescence intensity in cells that were incubated for 20 minutes

with 400µM 2-NBDG and DMEM (-) glucose with and without the addition of serum.

12

Figure 6: 200,000 4T07 cells were plated in 35mm glass bottom dishes and cultured for 24

hours prior to use. A Nikon (Melville,NY) Eclipse ti-s inverted microscope fitted with a DS-fi2

camera was used for image collection. 2-NBDG has an EX/EM of 465/540nm respectively. A)

4T07 cells incubated for 20 minutes with 400µM 2-NBDG in DMEM (-) glucose with the

addition of 10% serum. B) 4T07 cells fasted for 50 minutes with 400µM 2-NBDG in DMEM (-)

glucose with the addition of 10% serum. C) 4T07 cells fasted for 80 minutes with 400µM 2-

NBDG in DMEM (-) glucose with the addition of 10% serum. D) 4T07 cells incubated for 20

minutes with 400µM 2-NBDG in DMEM (-) glucose in absence of serum. E) 4T07 cells fasted

for 30 minutes with 400µM 2-NBDG in DMEM (-) glucose in absence of serum.

Between images A, B, and C in Figure 6 there wasn’t a significant difference in 2-NBDG uptake

and similarly between images D and E in the absence of serum. This is shown by the

fluorescence intensity histograms in Figure 7 and Figure 8. In Figure 7, the 2-NBDG uptake by

the 4T07 cells was highest with 20 min fasting in DMEM (-) glucose in the presence of 10%

serum. In Figure 8, there wasn’t a significant difference between the 4T07 cells fasted for 20

minutes or 30 minutes in the absence of serum. The cells were not fasted past 30 minutes due to

the cell viability issues in the absence of serum indicated in Figure 3.

WIT

H S

ERU

M

NO

SER

UM

A

D

B

E

C

t = 20 min

t = 20 min

t = 50 min

t = 30 min

t = 80 min

13

Figure 7: Histogram of 2-NBDG uptake of 4T07 cells fasted for 20, 50, and 80 minutes with

10% serum.

Figure 8: Histogram of 2-NBDG uptake of 4T07 cells fasted for 20 and 30 minutes in absence

of serum.

14

Conclusions: The 4T07 cell viability was significantly decreased by 60 minutes of fasting cells in

DMEM (-) glucose in the absence of serum as indicated in Figure 3. The addition of 10% serum

to the DMEM (-) glucose prolongs the fasting range to at least 150 minutes. The addition of 10%

serum allows for an adequate fasting window to optimize 2-NBDG uptake.

400µM 2-NBDG was determined to be the ideal concentration to optimize cell viability.

Figure 4 shows that for a concentration of 400µM of 2-NBDG there wasn’t a significant

difference in cell viability of the cells in both DMEM (-) glucose and DMEM (+) glucose in the

absence of serum. It is believed this is because the cells metabolize the high concentration of 2-

NBDG into 2-NBDG-6-Phosphate and in doing so it preserves the cell viability.

2-NBDG uptake is higher with the addition of serum to DMEM (-) glucose in 20 minute

fasting conditions (Figure 5). Figure 7 and Figure 8 show no significant evidence to suggest

that cells should be fasted beyond 20 minutes. Fasting beyond 20 minutes showed decreased 2-

NBDG uptake in the presence of 10% serum and no difference in the absence of serum.

It is recommended that before any study is begun a cell viability study during fasting

conditions be conducted. This will give an idea of the glucose dependency of the cell line which

helps to gauge the appropriate fasting duration. In the absence of serum, the 4T07 cell viability

was significantly decreased after 30 minutes of fasting. It is believed this is why the maximum

uptake was observed in both conditions ((+/-) serum) at 20 minutes of fasting (Figure 7 and

Figure 8). 400µM of 2-NBDG is the recommended concentration of 2-NBDG to maximize cell

viability and thus 2-NBDG uptake for the reasons discussed prior. It is also recommended that

serum be added to the fasting media to increase cell viability and 2-NBDG uptake (Figure 5).

15

The facts discussed above answer the proposed questions of the study. These guidelines

will hopefully provide clarity to the scientific community interested in using 2-NBDG for in

vitro studies.

Future Directions:

2-NBDG concentration vs. cell viability in 10% serum conditions will need to be

evaluated. This is to validate the belief that there isn’t a significant difference in cell viability for

all concentrations of 2-NBDG with the addition of serum. Microscopy images for increasing

concentration of 2-NBDG in both (+/-) serum conditions will need to be evaluated to confirm

that 400µM is the ideal concentration for maximum uptake.

To further validate that the addition of 10% serum to the fasting media increases 2-

NBDG uptake, images will need to be collected for all fasting time points (30 minutes, 60

minutes, 90 minutes, etc.) with and without serum.

The 4T07 cell line is very glucose dependent; this may impact the 2-NBDG uptake. To

confirm that the above findings are true for all cell types other cell lines will need to be evaluated.

A549 lung cancer cells would be ideal because of the OXPHOS leaning metabolism. The direct

comparison of these cells lines of varying glycolytic demand will provide a basis for researchers

to maximize 2-NBDG uptake in all types of cells based on their bioenergetic profile.

Upon completion of In Vitro murine studies In/Ex Vivo 2-NBDG uptake should be

investigated. Balb/cfC3H cells will be injected into mice to induce tumor formation. The tumors

will then be harvested as an Ex Vivo tissue and fasted according to the determined optimal In

Vitro protocol. 2-NBDG will then be introduced to the sample for 20 minutes. The Ex Vivo tissue

will then be imaged using fluorescence microscopy.

16

Acknowledgements

I would like to thank Dr. Priya Puvanakrishnan and Dr. Narasimhan Rajaram for their

support and guidance of this project. I would also like to thank the Department of Biomedical

Engineering at the University of Arkansas at Fayetteville for their funding of this research. I

would also like to acknowledge the University of Arkansas Honors College for their funding of

this research through the Honors College Research Grant.

17

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18

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19

Appendix A

Supporting Data:

Cell Viability

Figure 9: 4T07 cell viability for varying fasting durations in the absence of serum

Figure 10: 4T07 cell viability for varying fasting durations in the absence of serum

20

2-NBDG Concentration vs. Cell Viability:

Figure 11: 4T07 cell viability for varying 2-NBDG concentrations at 30 minute fast in absence

of serum.